三氮二氧配位基具三級丁基或氫取代基三價鐵超氧錯合物之碳氫鍵活化研究

Abstract

在自然界中，細胞色素 P450 (cytochrome P450) 與 IPNS (isopenicillin N synthase) 等酵素，可藉由氧氣的活化進行許多的催化反應，催化過程中產生的超氧與過氧化氫中間體是非常重要的一環，可將烷類氧化成醇類。 本研究使用實驗室所開發的 N3O2 五牙基 H2BDPRP(R = tBu, H) 配位基，經由去質子化並與 FeCl2 反應形成 Fe(BDPRP) ，其可與氧氣反應形成 Fe(BDPRP)(O2•) ，加入不同反應物後，可利用氣相層析質譜儀、紫外光/可見光光譜儀、核磁共振光譜儀與循環伏安法進行反應追蹤。 Fe(BDPRP)(O2•) 再加入三氟甲磺酸 (trifluoromethane-sulfonic acid, HOTf) 可藉此形成 Fe(BDPRP)(OOH) ，並得到其 pKa 為 10.79, 10.48(R = tBu, H)，再利用循環伏安法可求得其氧化還原半電位為 0.323, 0.276 V(R = tBu, H) ，使用上述測得的兩個數值定出 Fe(BDPRP)(OOH) 的鍵能為 82.7, 81.1 kcal/mol(R = tBu, H) 。再利用 Fe(BDPRP)(O2•) 與不同反應物進行 C−H 鍵活化，並進行定性與定量的研究。 上述研究可幫助我們更詳細的了解氧合酶之含金屬酵素進行碳氫鍵活化的反應機制與反應性的探討。

In nature, enzymes such as cytochrome P450 and isopenicillin N synthase can catalyze many reactions through the activation of oxygen, and the intermediate formation of superoxo and hydrogen peroxo species is a crucial part of the catalytic process, which can convert alkanes into alcohols. This study used N3O2 pentadentate H2BDPRP (R = tBu, H) ligands developed in the laboratory, which reacted with FeCl2 to form Fe(BDPRP) after deprotonation. The resulting Fe(BDPRP) can react with oxygen to form Fe(BDPRP)(O2•). By adding different reactants, the reaction was monitored using gas chromatography-mass spectrometry(GC-MS), UV-visible spectrophotometry(UV), nuclear magnetic resonance(NMR), and cyclic voltammetry(CV). Fe(BDPRP)(O2•) was then treated with trifluoromethane-sulfonic acid (HOTf) to form Fe(BDPRP)(OOH), and its pKa was obtained. The oxidation-reduction potential of Fe(BDPRP)(OOH) was determined by cyclic voltammetry, and the bond energy of Fe(BDPRP)(OOH) was determined using the two values obtained above. The C-H bond activation of Fe(BDPRP)(O2•) was studied qualitatively and quantitatively with different reactants. This study helps us to understand in detail the reaction mechanism and reactivity of metal-containing enzymes in oxygenases that catalyze C-H bond activation.